KR20040052121A - Liquid Crystal Display Device Having Variable Viewing Angle - Google Patents

Abstract

According to the present invention, first and second substrates facing each other and spaced apart from each other, a pixel electrode formed on an inner surface of the first substrate, a common electrode formed on an inner surface of the second substrate, and the pixel A first liquid crystal cell comprising a first liquid crystal layer interposed between the electrode and the common electrode; Third and fourth substrates facing each other and spaced apart from each other, a first alignment layer formed on an inner surface of the third substrate and oriented in a holographic pattern shape, and formed on an inner surface of the fourth substrate and holographic; A second liquid crystal cell composed of a second alignment layer oriented in a pattern shape and a second liquid crystal layer interposed between the first and second alignment layers and formed on the first liquid crystal cell; A liquid crystal display device having a variable viewing angle connected to the second liquid crystal cell and including a switching unit selectively applying an electric field to the second liquid crystal layer is provided.

Description

Liquid Crystal Display Device Having Variable Viewing Angle

The present invention relates to a liquid crystal display device, and more particularly, to a liquid crystal display device and a method of manufacturing the same that can change the viewing angle.

Until recently, cathode ray tube (CRT) has become the mainstream of display devices and has been continuously developed. Recently, the necessity of flat panel display is needed to meet the times of miniaturization, light weight and low power consumption. It has emerged. Accordingly, a thin film transistor-liquid crystal display device (hereinafter referred to as TFT-LCD) having excellent color reproducibility has been developed, and the size of the liquid crystal display device is gradually increasing in size. It is a trend.

Here, the configuration of the liquid crystal display device will be described.

1 is an exploded perspective view showing a conventional liquid crystal display device.

As shown in FIG. 1, the conventional liquid crystal display 11 includes a color filter 7 including a black matrix 6, an upper substrate 5 on which a transparent common electrode 18 is formed on a color filter, And a lower substrate 22 including a pixel electrode 17 and a switching element T formed in the pixel region P. A liquid crystal layer 14 is inserted between the upper substrate 5 and the lower substrate 22. have.

The lower substrate 22 is also called an array substrate, and the thin film transistor T, which is a switching element, is positioned in a matrix type, and the gate line 13 and the data line 15 passing through the plurality of thin film transistors are intersected. Is formed.

In this case, the pixel P area is an area where the gate line 13 and the data line 15 cross each other.

The portion consisting of the upper and lower substrates 5 and 22 and the liquid crystal layer 14 interposed therebetween is also referred to simply as a liquid crystal cell or a liquid crystal panel.

Recently, the liquid crystal cell mainly used is a twisted nematic LC (hereinafter referred to as a TN liquid crystal) cell. The liquid crystal molecules forming the TN liquid crystal cell have a thin long rod shape and have a constant pitch in a spiral shape. Twisted has a twisted structure in which the direction of arrangement of the long axis of the liquid crystal molecules changes continuously.

In this TN method, the incident polarization shows different viewing angle characteristics depending on the arrangement of the long and short axes of the molecules.

That is, since the viewing angle of the liquid crystal display is formed along the long axis of the liquid crystal molecules of the spiral structure, the viewing angle changes according to the viewing direction.

The liquid crystal display has a symmetrical viewing angle in the range of +45 to -45 with respect to the horizontal direction and a viewing angle is limited between -15 and 5 degrees with respect to the vertical direction, so that the image is inverted in the vertical viewing angle. There is a problem that the viewing angle is narrowed.

When the LCD is small, a small number of users will often look at the LCD from a limited angle, but as the LCD becomes larger, it is more likely that many users will see the LCD from different angles. Accordingly, the limited viewing angle characteristic of the liquid crystal display device is an important problem.

In order to overcome the limited viewing angle problem of the liquid crystal display, a film-compensated mode using a compensating film or a diffusing film and a pixel are divided into several domains. Multi-domain mode, which compensates the viewing angle by changing the direction of viewing angle of each domain, and IPS mode, which applies a transverse electric field by placing two electrodes driving liquid crystal on one plane. ) Has been proposed.

In this case, when the wide viewing angle liquid crystal display device having an extended viewing angle is required for security, for example, when used in a CD screen of a bank, it is necessary to have a narrow viewing angle according to a user's selection. The display device has a disadvantage in that only a wide viewing angle can be implemented.

In order to solve the above-mentioned problems, the present invention uses a holographic cell oriented in a holographic pattern to implement an image at a narrow viewing angle for a small number of users and a wide viewing angle for a large number of users. It is an object of the present invention to provide a liquid crystal display and a manufacturing method thereof.

1 is an exploded perspective view showing a conventional liquid crystal display device.

2 is a schematic cross-sectional view showing a liquid crystal display device having a variable viewing angle according to the present invention.

3A is a schematic plan view showing a second liquid crystal cell according to the present invention when no electric field is applied.

3B is a schematic plan view showing a second liquid crystal cell according to the present invention when an electric field is applied.

4A is a schematic cross-sectional view showing a cut along the line IVa-IVa of FIG. 3A.

FIG. 4B is a schematic cross-sectional view showing a plane cut in accordance with IVb-IVb of FIG. 3B. FIG.

<Description of Symbols for Major Parts of Drawings>

110: first substrate 120: second substrate

130: first liquid crystal layer 170: second liquid crystal layer

150: third substrate 160: fourth substrate

140: first polarizer 180: second polarizer

LC1: first liquid crystal cell LC2: second liquid crystal cell

In order to achieve the above object, the present invention is formed on the first and second substrates facing each other and spaced apart from each other, the pixel electrode formed on the inner surface of the first substrate, and the inner surface of the second substrate A first liquid crystal cell comprising a common electrode, and a first liquid crystal layer interposed between the pixel electrode and the common electrode; Third and fourth substrates facing each other and spaced apart from each other, a first alignment layer formed on an inner surface of the third substrate and oriented in a holographic pattern shape, and formed on an inner surface of the fourth substrate and holographic; A second liquid crystal cell composed of a second alignment layer oriented in a pattern shape and a second liquid crystal layer interposed between the first and second alignment layers and formed on the first liquid crystal cell; A liquid crystal display device having a variable viewing angle connected to the second liquid crystal cell and including a switching unit selectively applying an electric field to the second liquid crystal layer is provided.

A first electrode formed between the third substrate and the first alignment layer and a second electrode formed between the fourth substrate and the second alignment layer may be further included, and the switching unit may be disposed on the first and second electrodes. Connected.

The switching unit includes a voltage source and a switch, and the third and fourth substrates may be made of glass, plastic, or resin.

The third and fourth substrates may be in the form of a flexible adhesive film, and the first and second alignment layers may be oriented in a vertical, horizontal or hybrid manner.

An outer first polarizer of the first substrate and a second polarizer may be further included on an outer surface of the fourth substrate, and a backlight may be further included below the first liquid crystal cell.

On the other hand, the present invention, the first substrate; A pixel electrode formed on the first substrate; A first liquid crystal layer formed on the pixel electrode; A common electrode formed on the first liquid crystal layer; A second substrate formed on the common electrode; A third substrate formed on the second substrate; A first alignment layer formed on the third substrate and oriented in a holographic pattern; A second liquid crystal layer formed on the first alignment layer; A second alignment layer formed on the second liquid crystal layer and oriented in a holographic pattern; A fourth substrate formed on the second alignment layer; Provided is a liquid crystal display having a variable viewing angle including a switching unit for selectively applying an electric field to the second liquid crystal layer.

Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings.

2 is a schematic cross-sectional view of a liquid crystal display having a variable viewing angle according to the present invention.

As shown in FIG. 2, the first and second substrates 110 and 120 face each other and are spaced apart from each other, and the first liquid crystal layer 130 is inserted between the first and second substrates 110 and 120. have. The first and second substrates 110 and 120 and the first liquid crystal layer 130 form a first liquid crystal cell LC1.

Although not illustrated, a thin film transistor (TFT) and a pixel electrode may be formed on an inner surface of the first substrate 110, and a color filter and a common electrode may be formed on an inner surface of the second substrate 120.

The first polarizer 140 is formed on the outer surface of the first substrate 110. Although not shown, a backlight is configured under the first polarizer 140 to supply light.

The second liquid crystal cell LC2 is formed on the outer surface of the second substrate 120, and the second polarizer 180 is formed on the second liquid crystal cell LC2. The second liquid crystal cell LC2 includes third and fourth substrates 150 and 160 and a second liquid crystal layer 170 interposed therebetween.

Although not shown, first and second electrodes are formed on inner surfaces of the third and fourth substrates 150 and 160, respectively, and the first and second electrodes are connected to an external switch S and a voltage source Vg. In this case, the external switch S and the voltage source Vg are one example, and means for selectively applying an electric field to the second liquid crystal layer 170 as necessary may be connected to the second liquid crystal cell LC2. Will be enough.

In addition, an alignment layer (not shown) is formed on the first and second electrodes, respectively. Each alignment layer is aligned using a holographic pattern. In this case, an effect of diffusing light is generated by the interference pattern.

However, when the electric field is applied to the second liquid crystal layer 170, since the second liquid crystal layer 170 is aligned horizontally or vertically regardless of the alignment direction, the light diffusion effect is not exhibited.

The third and fourth substrates 150 and 160 may be made of glass, plastic, or resin. The third and fourth substrates 150 and 160 may be made of glass, plastic, or resin. The third and fourth substrates 150 and 160 may be formed in an adhesive film by forming an electrode and an alignment layer on one surface of the flexible film and coating an adhesive material on the other surface. Do.

Referring to the operation of the liquid crystal display illustrated in FIG. 2, the first liquid crystal cell LC1 drives the pixel electrode and the common electrode of each pixel according to the gate signal and the data signal, thereby emitting light having a narrow viewing angle from the second liquid crystal cell ( LC2).

The second liquid crystal cell LC2 supplied with the narrow viewing angle light from the first liquid crystal cell LC1 is used in two modes.

When it is necessary to implement a wide viewing angle image, for example, when a large number of users look at the liquid crystal display from various angles, the switch S is turned off and used. When the switch S is turned off, since the voltage is not supplied from the voltage source Vg to the second liquid crystal cell LC2, the second liquid crystal layer 170 oriented in the holographic pattern is aligned in the oriented direction to diffuse light. Do it.

On the other hand, when it is necessary to implement an image of a narrow viewing angle, for example, when a few users look at the liquid crystal display from a limited angle, the switch S is turned on and used. When the switch S is turned on, since the voltage is supplied from the voltage source Vg to the second liquid crystal cell LC2, the second liquid crystal layer 170 oriented in the holographic pattern is aligned horizontally or vertically regardless of the oriented direction. To pass light in a constant direction.

Therefore, the user can change and use the viewing angle of the liquid crystal display as needed.

The second liquid crystal layer 170 oriented in the holographic pattern will be described in detail with reference to the drawings.

3A and 3B are schematic plan views showing a second liquid crystal cell according to the present invention when an electric field is not applied and when an electric field is applied, respectively. FIGS. 4A and 4B are IVa-IVa and 3B of FIG. 3A, respectively. Is a schematic cross sectional view showing a plane cut along IVb-IVb.

3A, 3B, 4A, and 4B, the second liquid crystal cell LC2 includes third and fourth substrates 150 and 160 facing each other and spaced apart from each other. First and second alignment layers 152 and 162 are formed on inner surfaces of the third and fourth substrates 150 and 160, respectively, and a second liquid crystal layer 170 is disposed between the first and second alignment layers 152 and 162. Is inserted. The second polarizer 180 is formed on the outer surface of the fourth substrate 160.

Although not shown, first and second electrodes are formed between the third substrate 150 and the first alignment layer 152 and between the fourth substrate 160 and the second alignment layer 162, respectively. Is connected to an external switch (S in FIG. 2) and a voltage source (Vg in FIG. 2) to apply an electric field to the second liquid crystal layer 170 as necessary. In some cases, the first and second electrodes may be formed on outer surfaces of the third and fourth substrates 150 and 160.

Meanwhile, the first and second alignment layers 152 and 162 are aligned in a holographic pattern. That is, the second liquid crystal cell LC2 has first and second regions A and B oriented differently from each other. In this case, each of the alignment layers 152 and 162 may be aligned in a vertical, horizontal, or hybrid manner.

As shown in FIGS. 3A and 4A, when the electric field is not applied, the liquid crystals are aligned according to the alignment direction, so that the second liquid crystal layers 170 of the first and second regions A and B are aligned in different directions. Therefore, the light passing through the second liquid crystal cell LC2 is represented by a holographic pattern. In this case, the thickness (modulation depth d ′) of the second liquid crystal layer 170 felt by the interference pattern is actually the second. Since the thickness d of the liquid crystal layer 170 is different and the retardation d′ Δn is also different from the actual phase difference dΔn, light is diffused to implement a wide viewing angle.

As shown in FIGS. 3B and 4B, when an electric field is applied, the liquid crystals are aligned horizontally or vertically regardless of the alignment direction, so that the second liquid crystal layer 170 of the first and second regions A and B is in one direction. Aligned. Therefore, the second liquid crystal cell LC2 does not diffuse light and maintains the narrow viewing angle of the first liquid crystal cell (LC1 of FIG. 2).

Therefore, in the liquid crystal display having the variable viewing angle according to the present invention, the viewing angle may be expanded or reduced according to the needs of the user.

A liquid crystal display having a variable viewing angle and a method of manufacturing the same according to the present invention are not limited to the above embodiments, and various modifications may be made by those skilled in the art to which the present invention pertains without departing from the spirit of the present invention. It is apparent that variations and modifications are possible, and it is apparent from the appended claims that such variations and modifications belong to the present invention.

As described above, in a liquid crystal display having a variable viewing angle, the viewing angle is extended by forming a second liquid crystal cell oriented in a holographic pattern on top of the first liquid crystal cell and optionally applying an electric field to the second liquid crystal cell. Or there is an advantage that can be reduced.

Claims (10)

First and second substrates facing each other and spaced apart from each other, a pixel electrode formed on an inner surface of the first substrate, a common electrode formed on an inner surface of the second substrate, and common to the pixel electrode. A first liquid crystal cell comprising a first liquid crystal layer interposed between the electrodes; Third and fourth substrates facing each other and spaced apart from each other, a first alignment layer formed on an inner surface of the third substrate and oriented in a holographic pattern shape, and formed on an inner surface of the fourth substrate and holographic; A second liquid crystal cell composed of a second alignment layer oriented in a pattern shape and a second liquid crystal layer interposed between the first and second alignment layers and formed on the first liquid crystal cell; A switching unit connected to the second liquid crystal cell and selectively applying an electric field to the second liquid crystal layer Liquid crystal display having a variable viewing angle comprising a. The method of claim 1, And a second electrode formed between the third substrate and the first alignment layer, and a second electrode formed between the fourth substrate and the second alignment layer. The method of claim 2, And the switching unit is connected to the first and second electrodes. The method of claim 1, And the switching unit comprises a voltage source and a switch. The method of claim 1, And the third and fourth substrates are made of glass, plastic, or resin. The method of claim 5, wherein And the third and fourth substrates are in the form of a flexible adhesive film. The method of claim 1, And the first and second alignment layers are aligned in a vertical, horizontal, or hybrid manner. The method of claim 1, And a second polarizer formed on the outer surface of the first substrate and a second polarizer formed on the outer surface of the fourth substrate. The method of claim 1, The liquid crystal display of claim 1, further comprising a backlight disposed under the first liquid crystal cell. A first substrate; A pixel electrode formed on the first substrate; A first liquid crystal layer formed on the pixel electrode; A common electrode formed on the first liquid crystal layer; A second substrate formed on the common electrode; A third substrate formed on the second substrate; A first alignment layer formed on the third substrate and oriented in a holographic pattern; A second liquid crystal layer formed on the first alignment layer; A second alignment layer formed on the second liquid crystal layer and oriented in a holographic pattern; A fourth substrate formed on the second alignment layer; Switching unit for selectively applying an electric field to the second liquid crystal layer Liquid crystal display having a variable viewing angle comprising a.